Tad Cook, K7RA, in Seattle, reports: The current stretch of spotless days is now over 3 weeks, according to Spaceweather.com. The continuing quiet seems eerie. For this past reporting week, Thursday through Wednesday, the average daily solar flux (10.7 GHz radiation recorded in Penticton, British Columbia, which roughly tracks with sunspot activity) was only 66. I couldn’t recall when the weekly average reported in this bulletin was last that low, and couldn’t find any report during the past year with such low activity.

I did an inspection of the numbers and had to go back to the fall of 2007 to find average solar flux in that range. In 2007 we reported an average of 66.5 in bulletin number 40. Can anyone else find solar flux that low or lower in past bulletins? We have them online going back to 1995.

If anyone has copies of propagation bulletins prior to 1995, I would love to see them. I began writing the bulletin in March 1991. Before that, W1HDQ (SK) was the author. I recall copying the bulletin as a teenager in 1966 on CW but have not found anyone who knows when the bulletin began.

Predicted solar flux for the next 45 days is 66 on August 30 – September 6; 67 on September 7 – 11; 68 on September 12 – 15; 67 on September 16 – October 8; 68 again on October 9 – 12, and 67 on October 13.

Predicted planetary A index is 8, 20, 34, 16, and 8 on August 30 – September 3; 5 on September 4 – 5; 8 on September 6 – 7; 5 on September 8 – 21; 10, 15, and 8 on September 22 – 24; 5 on September 25 – 27; 35, 18, and 10 on September 28 – 30; 5 on October 1 – 2; 10 and 8 on October 3 – 4, and 5 on October 5 – 13.

Note that the predicted planetary A index is 34 on September 1, which according to W3LPL and The ARRL Letter is the 160th anniversary of the infamous Carrington Event.

Spaceweather.com reported a large recurring coronal hole facing Earth and expects the effects to be felt on Sunday, September 1. A planetary A index value of 35 is predicted for the next solar rotation, on September 28.

Geomagnetic activity forecast for the period August 30 – September 26 from OK1HH. The geomagnetic field will be:

• Quiet on: September 10 – 11, 20 – 21, (25 – 26)

• Quiet to unsettled on: August 30, September 3 – 5, 7 – 8, 13, 17, 22, 24

• Quiet to active on: August 31, September 6, 9, 12, 14 – 16, 18 – 19, 23

• Unsettled to active on: September 2

• Active to disturbed: September 1

• Solar wind will intensify on August (30) – 31, September 1 ( – 2), (4 – 6)

[Parenthesis means lower probability of activity enhancement.]

For more information concerning radio propagation, visit the ARRL Technical Information Service, read “What the Numbers Mean…,” and check outK9LA’s Propagation Page.

A propagation bulletin archive is available. Monthly charts offer propagation projections between the US and a dozen DX locations.

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Sunspot numbers for August 22 – 28 were 0, 0, 0, 0, 0, 0, and 0, with a mean of 0. The 10.7 centimeter flux was 65.7, 66.5, 66.3, 66, 65.8, 66.1, and 65.9, with a mean of 66. Estimated planetary A indices were 6, 4, 5, 4, 6, 10, and 5, with a mean of 5.7. Middle latitude A index was 7, 4, 5, 5, 6, 10, and 5, with a mean of 6.

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